Nickel-alloy



United States Patent 3,188,204 NICKEL-ALLOY Claude R. Bishop, Niagara Falls, and William I. Boesch, Utica, N.Y., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed Apr. 8, 1963, Ser. N 271,488 Claims. (Cl. 75-170) This invention relates to a nickel-base alloy characterized by stability in oxidizing environments and by superior creep rupture properties at elevated temperatures.

Progress in the field of hypersonic aircraft and missiles has brought to light a number of problems relating to materials of construction. One such problem, to which no satisfactory solution has been evidenced in the past, is that of aerodynamic heating, i.e., heating caused by the friction of the atmosphere on the surface of an object travelling at high speeds. This phenomenon is associated with aircraft which operate at or near supersonic speeds. This particular problem is even more pronounced when the object is a missile or other space vehicle the trajectory of which carries it out of the atmosphere and back again. Re-entry into the atmosphere at hypersonic speeds subjects the outer surface of the object to extremely rapid heating and substantial stress. It is obvious that there is a present need for alloys which are capable of withstanding these extreme conditions.

Another problem encountered in connection with missiles is the need for a material which is suitable for use in oxidizing environments, e.g., fuming nitric acid which is used to oxidize fuels in rocket engines.

The problem of oxidation resistance is not unique to the missile field. Another field where stability in corrosive environments is important is in the construction of chemical processing equipment. In this particular field corrosion resistance combined with strength and ductility is of primary importance.

Moreover to be useful for such applications as the outer skin of a missile, or a component of a gas turbine these alloys must be amenable to known methods of fabrication and forming.

It is therefore an object of this invention to provide a nickel-base alloy which exhibits superior creep-rupture properties at elevated temperatures.

It is another object of the invention to provide a nickelbase alloy which possesses a high degree of stability to corrosion when exposed to oxidizing environments at elevated temperatures.

It is a further object of the invention to provide a nickel-base alloy which combines superior creep-rupture resistance and which can be forged and rolled into various forms and thin sheets.

These and other related objects are achieved by providing an alloy comprising, along with incidental impurities, at least 25 weight percent nickel, 1 to 25 weight percent tantalum, to 50 weight percent tungsten, and a maximum of 0.5 weight percent carbon;

Additional highly desirable alloys are obtained by the addition, to the above composition, of selected amounts of at least one metal chosen from the group comprising, iron, aluminum, molybdenum, and chromium.

Iron, aluminum, molybdenum, and chromium in se- 12 weight percent; aluminum, from about 1 to about 5 weight percent; molybdenum, from about 5 to about 15 weight percent; and chromium, from about 8 to about 20 weight percent. The above stated ranges may conveniently be referred to as selected amounts of the particular metal.

An alloy which is particularly corrosion resistant comprises 24 to 50 weight percent tungsten, 5 to 15 weight percent tantalum, at least weight percent nickel, a maximum of 0.15 weight percent carbon, incidental impurities, and at least one additive selected from the group comprising 4 to 10 weight percent iron, 1 to 5 weight percent aluminum, 5 to 15 weight percent molybdenum, and 8 to 15 weight percent chromium.

An alloy evidencing enhanced creep-rupture resistance comprises, along with normally present impurities, 20 to weight percent tungsten, 1 to 20 weight percent tantalum, at least 35 weight percent nickel, a maximum of 0.15 weight percent carbon and at least one additive selected from the group comprising 1 to 2 weight percent aluminum, 8 to 20 weight percent chromium, and 5 to 15 weight percent molybdenum.

The most preferred alloy satisfying the above-mentioned corrosion-resistance objects comprises 24 to weight percent tungsten, 5 to 15 weight percent tantalum, up to 10 weight percent iron, up to 5 weight percent aluminum, up to 15 weight percent molybdenum, upto 15 weight percent chromium, a maximum of about 0.5 weight percent carbon, the balance at least 40 weight percent nickel and the remainder incidental impurities.

The most preferred alloy satisfying the above-mentioned creep-rupture resistance at high heating rate and at high temperatures comprises 20 to about 45 weight percent tungsten, 1 to 20 weight percent tantalum, up to about 2 weight percent aluminum, up to about 20 weight percent chromium, up to about 15 weight percent molybdenum, a maximum of about 0.5 weight percent carbon, the balance at least 35 weight percent nickel and the remainder incidental impurities.

Creep is the flow or plastic deformation of metals held at stresses lower than the normal yield strength. The conventional creep-rupture test normally consists of submitting a specimen to a constant tensile load or stress at a constant ambient temperature and up to about 1000 C. for given periods of time and measuring the total creep in inches per inch at given times. These parameters are plotted against one another to obtain a tensile creep curve. Tests of this type are especially useful in ascertaining the creep-rupture characteristic of metals at ambient temperature and up to about 1000 C. because the time of application of stress is very long before rupture is experienced. The final result of the above creep lected amounts have been found to exert a desirable efture strength, corrosion resistance, and the like can be achieved.

In general the additive metals are employed in amounts within the following ranges: iron, from about 4 to about rupture test will be a creep-rupture index denoting minute fractions of an inch creep per inch of original specimen length per thousands of hours at ambient temperatures.

An artisan selects a proper material by correlating a fixed permissible deformation and required service time with the creep-rupture index of tested materials to decide which materials are amenable to his specific purpose.

The conventional creep rupture test has been used herein at an elevated temperature of approximately 1000" C. A creep-rupture index was obtained, which due to the short total life of the specimen before rupture, is of necessity expressed in total hour-life before rupture.

Conventional tests, however, are obviously unsuited to properly evaluate materials which are to be subjected to the severe conditions imposed by re-entry of a missile into the atmosphere for example. Materials operating under these conditions are shocked by an abrupt application of havior under these conditions cannot be predicted by the results of conventional creep-rupture tests; therefore, special tests have been devised which are characterized by sistance to reducing media such as hydrochloric acid and moderately low concentrations of sulfuric acid.

Included within Table I are test results obtained by subjectin" commercially available alloys to the same enshort duration, high temperature, and rapid heating rates 5 vironrnents as the alloy of this invention. which closely simulate thetype of conditions actually en- From the data presented in Table I, it may be seen that countered by missiles andthe like. Since extremely high the alloy composition range for maximum corrosion retemperatures are employed in the special tests, the creepsistance is between about 25 to 50 weight percent tungrupture life in these tests is considerably reduced for all sten, 5 to 15 weight percent tantalum and the balance nickmetals and is expressed in total life-minutes before rupel and incidental impurities, with the alloy containing a ture. The alloys of thepresent invention exhibit surprisminimum of about 40 Weight percent nickel. ing creep-rupture resistance under the special creep-rup- The stress-rupture properties of the alloy of this inture tests. vention were determined under conditions of rapid heat- The superior corrosion resistant properties or the alloy ing. The specimens were heated to a testing temperature of this invention to the corrosive attack of highly oxidizof about 2300 at a'rate approximately 150 F. per ing media is evidenced by'tests in which samples of the second during which time they were subjected tovarious alloy were subjected to the action of several corrosive amounts of stress. The results of these tests are set forth solutions such as boiling, fuming nitric acid, and its conin Table II, III, IV and "V. The alloys of this invention, densate. The results of these tests'are set forth in Table under conditions of rapid heating, possessed stress-rupture I. These samples were subjected to boiling fuming nitric properties far superior'to 'prior'art alloys. The results acid condensate for an average of at least three 48-hour ol rapid-heating rate, creep-rupture tests on prior art periods. The remainder of the data indicates that the alloys are included in Table VI. The alloys of Table II, alloy of this invention also has improved corrosion re- III, IV, V and VI contain incidental impurities.

Table I Composition, weight percent Mils per. year Boiling fuming nitric acid Boiling sulfuric acid W Ni Ta 0 condensate Boiling 65% Boiling Boiling 10% nitric acid 20% I101 chromic acid .84 0. 002 2, 100 9, 970 153 351 4, 300 5, 500 so. 1 4. 5 05 0. 003 420 9, 750 109 523 559 1, 730 54. 5 10. 44 .95 0. 004 50.3 7, 500 498 792 388 1, 559 71. 5 14. 51 .50 0. 001 5. 0 2, 510 117 55. 5 240 1, 150 94. 7 25. 05 77 0. 003 1. 51 522. 0 15.8 57. 3 53. 0 549 437 23. 75 10. 54 0.040 0. 57 3. 43 8. 9 2s. 8 53. 1 525 53. 5 24. 00 15. 51 0. 010 0. 25 1. 5. 15 15. 8 40. 0 452 33. 7 24. 95 21. 01 0. 025 23.1 21.5 52. 2 25. s 251 174 31. 52 4. 59 0. 0.25 1. 30 15.7 19. s 50. 5 15. 0 407 79. s 33. 9. 03 0. 055 0. 59 3. 55 12. 2 18. 4 44. 0 435 75. 5 45. 01 5. 0. 025 0. 57 4. 19 5. 57 29.7 15. 9 355 117 42. 54 11.12 0. 014 0. 24 1. 73 19.5 29.4 51. 0 385 81.1

Commercially available alloy 0.07, 18 Cr., 8 Ni., balance iron--. 1, 2 0 10. 0 20 Cr. 29 Ni., 2.0 M0., 3 (311., balance iron--. 43. 0 38.0 143 Table II Stress, p.s.i. at 1, 250 C.

Percent Percent Percent Percent 3,000 4,000 5,000 6,000

W Ta Ni 0 WWW. Min. Percent Min. Percent Min. Percent Min Percent El. 1 El. E1.

T ablelll Stress, p.s.i. at 1,250 O.

Percent Percent Percent Percent 2,000 3,000 4,000 5,000 6,000

W Ta Ni 0 Min. Percent Min. Percent Min. Percent Min. Percent Min. Percent 1. El. E1. El.

4. 57 11.05 0. 003 125. 5 9. 5 5. 8 8.5 10. 44 9. 0. 004 9. 3 15.8 9. 5 4.10 s. 5 14.51 9. 50 0.001 7.5 25.2 9.5 Y 2.1 20. 44 9. 22 0. 024 24. 3 7. 5 10. 1 5. 5 4. 5 22. 45 7. 94 0. 904 35. 3 7. s 14.0 7. 5 5. 2 23. 7 10. 54 0. 040 5. 0 45. 9 5. 3 5.1

Table IV .E B e 50503 c E 77579 P 0 6 s .m 54 2m2 M 2455m t n 55 n u TE .66.. e n n n P 0 0 l 0 C 5 O 0 65 5 .m 2 I "BM u 1. n I t a. i m t m 38530 NE 6 06 00 6 e 1 H 0 P s D 4 m 964.97 .1 90 6 5 5 M 13244 m 0 u "0 M .L 7 .6 T e n n u 0 P 0 3 3 n 9 u H 1 3 M 7 .5 n-lt .n. hmam R 00000 e P 00000 m u a I... M 1 1 1:.. P aaaa m BBBBB t n 9456 WV 83070 565 H 222%% P 7 1 m %7M6 IT H e P TABLE V Stress, psi. at 1250 C.

t any!" 00050 C 0 1 M 1H1 0 P 0 6 m 11227 .1 5 7 00 3 M 1 t w 1 r E 0 P 0 5 .29 m .33 -11 m BL 30302 0 6 mm 6 0 P 0 w. 4

99385 507 3 m 4 223 t n 8L 050 0 C 1 E 6 "cc 0 P 0 0 3 83 m 953 5 3 3 .L5w7 M 7773 Percent Percent Percent Mo Al Table Vl.--High heating tests on prior art alloys at Table IX .Results of standard creep-rupture tests on temperature of 1250 C.

prior art alloys Weight percent composition 000 L w m m m m a 0 3m mm 1.5. m w L uao i O lnl. hmm m 0 00 0 en a.. m mm m m m mm .m n as 5 5 5 5 t m h I H D f S O p 6 3f. W dmm w 2 22 2 O I n L D... 8 88 no 1 O m 9 99 9 .n H n WISH es ao wn T Pun N I 1 mns v owmrm & e w w 3 .10 0 0 M 1 m l h 0 flfl t 9 5 m m N w. V. W. a 0 a pa... m m C m .we ba e o n. ohreul D. 5 D f. C V n 2 6 f hwv P r i .m mtm m 6 ON s M n C 2 itt 2 1. M nama L mflfle ww m n a c 0% a m w e e f n l 2. 0 Unmv 5 5 3 a 4 t H 6 5 0 m mw 3 5 9 7 H CH0 t amfi W P8 3 7 8 0 9 W mm 1 5 m 0e, c T m... 0 0 0 0 0 mat w m m mm m HS 3 2w 3w 3 3 I D n s s t 1 m e S a n n .P .m l m B e d .1 c H .1 d H a 0.05 c, 22 Cr, 2.5 00, Max., 6.5, 1.0 w,

2 Cb/Tn, Fe, balance Ni. .2 C Max, 22 CI, 2.0 Go, 9.0 M0, 0.7 W,

2.25 A1, balance Ni- .2 C Max., 21 Cr, Ni 20 Co, 3 M0, 2.5

W, l Cb/Ta, balance Fe 0.5 C Max., 1 Cr, 2.5 00. Max., 28 Mo., 5.5

Fe, balance Ni-- In addition, it has been found that a binary aJloy of about weight percent tungsten and the remainder nickel resistance as evidenced from the data in Table VII.

Table VII.Influence of tungsten the prior art alloys (Table VI) under rapid heating-creep- MW E 8 0 0 P 8 s .m M .9 m mL a m 0 P 0 6 n .1 i 5 M 2 .90 .7 C M 0 P 0 c 5 7 O m .4 9m. 1 t a t .M r ME .1 m 0 P U m m 4 .5 .m a M .7 t m. .0 e1 L 0 a... .1 0 P 3 a .3 .m 2 M .5 2 t n win E 0 P 0 2 H m a Ln P a BB m 1 m 90 {W 4TH e 44 P Table VIII includes data showing the results of conventional creep-rupture tests conducted on the alloys of rupture tests indicates the surprising superiority of the the present invention. Table 1X shows data resulting from present novel alloys.

conventional creep-rupture tests on prior art alloys. When the alloy of this invention is to be employed in an om'dizing media, such as 10 percent boiling chrornic Table VIIl.Results of standard creep-rupture tests on acid, the addition of chromium to the base alloy in amounts up to 20 percent with the preferred range being the alloys of the present invention about 10 percent, can reduce the corrosion rate to as little as 14.3 mils per year as shown in Table X and increase creep-rupture life as shown in Table V. In addition, where greater oxidation resistance is desired, for example, in cases Where the alloy is subjected to high temperatures for periods of time measured in hours rather than in minutes, chromium may be added without substantially detracting from the superior properties of the base-alloy as noted inTable XI.

To further illustrate the versatility of the alloys of the -gain in weight in grams per square invention, corrosion resistance, oxidation resistance, and rapid heating tests were conducted on a chromium-contain lustrated by reference to Table XII. Table XII shows the composition of three alloys cast under similar coning and molybdenum containing alloy of this invention.

An alloy consisting of 10.63 percent chromium, 9.99 percent tantalum, 25.83 .percent tungsten, 0.037 percent carbon and the balance nickel and incidental impurities was subjected to corrosion .tests in .10 .percent boiling chromic acid. The average corrosion rate, given in mils per'year, from five 48-hour periods was 143 as noted in the following Table X. The advantageous increase in corrosion resistance gained bythe addition of molybdenum andiron are also shown in Table X.

Table .X

Composition, Weight percent Corrosion rate, mils per year Boiling Boiling sulfuric acid Boiling 10% W N1 Ta Gr Mo Fe O fuming Boiling 65% .Boiling chromic nitric acid nitric acid H 01 acl condensate 10% 30% 55% An oxidation resistance .test was :conducted 50H an failure of alloys. 1 and 2 is attributed to the higher carbon alloy of the samecomposition as that subjected'to the corrosion resistance test above. The oxidation test was conducted at 1900 F. for a period of 113 hours. At the end of this period, the oxidation rate, expressed as inch, was 0.01 as noted in Table XI. 7

Table XI Alloys of present invention; percent Oxidation rate cxpressedzas gain in'weight c in grams/sq.

O W Ta Cr .Al Ni 111.1113 hrs.

' at 1900 F.

0.027 30. 04 Bal- 0. 123 0. 010 25: 89 Bal. 0. 115 0.012 46. 07 Ba1 0. 498 0. 010 23. 76 10.64 .Ba1 0.142 0.037 25. 83 9.99 10. 63 Bal 0.010 0. 071 26. 26 10.28 11. 61 1. 57 Bath 0. 014 0.080 24. 01 19. 92 i 1. 72 B211... 0.015

From these tests it can be seen that by the addition of certain other alloying materials to the nickel-base alloy certain desirable properties can be imparted to the alloy for certain specific purposes without substantially detracting from the very desirable combination of corrosion resistance, oxidation resistance, and high heating stress-rupture properties.

Iron may be present in the alloy of thisinvention in proportions as high as 10 percent by deliberate additions such as ferro-alloys,- e.g.,-fer-rotantalum. The results of such an addition are notedin Table X. However, for the best hot-working properties, the iron content, preferably,

should not exceed the quantity introduced as an impurity in the usual melting operation, which is generally on the order of 1.5 percent. Although iron seems'to increase corrosion resistance in some instances,.it has the concurrent effect of decreasing amenabi lity of the alloys to hot working.

Carbon,-which is a conventional impurity, maybe present in amounts up to a maximumef 0.5 weight percent. It is preferred however, that the carbon content be kept'aslow as possible. The carbon content of the alloy is particularly important with respect to the workability of the alloy. For the enhanced workability characteristics carbon contents of less than 0.15 are recommended. The most preferred al loys from the standpoint of workability are those which contain less than 0.12 weight percent carbon.

The influence o carbon content in workability is ilcontent.

alloy may be prepared by induction melting'the desired constituents in a vacuum furnace or under an atmosphere of an inertgas.

It may be seen thatthe unique combination of properties possessed by the alloy of thisinvention is very valuable in the missile field wherein at thepresenttime from the best information available a service life of 15 seconds is adequate, whereas, under otherconditions, a service life of 10 to 15 minutes may be required. The alloys of the present invention possess a creep-rupture life well in excess of the required life time presently thought to be required for missile service.

This application is a continuation-in-part of U5. Serial No. 61,084, filed October 7, 1960 and now abandoned.

What is claimed is:

1. An alloy consisting essentially of, along with incidental impurities, at least 25 weight percent nickel, l to 25 weight percent tantalum,'20 to 50 weight, percent tungsten, a'maximum of 0.15 weight percent carbon,.:and selected amounts of-at least one metal chosen fromv the group consisting of iron, aluminum, molybdenum and chromium.

2. An alloyconsisting essentially of, along with incidental impurities, at least 40 Weight percent nickel, *24 to 50 weight percent tungsten, 5 to 15 Weight percent tantalum, a maximum of 0.15 weight percent carbon, and selected amounts of at least one metal chosenfrorn the group consisting of iron, aluminum, molybdenum, and chromium.

3. An alloy consisting essentially of, along with incidental impurities, at least 35 weight percent nickel, 20 to 45 weightpercent tungsten, 1 to. 20 weight percent tantalum, avmaximum of 0.15 weight percent carbon, and selected amounts of at least one metal chosen from the groupconsisting of iron, aluminum, molybdenum, and chromium.

4. An alloy consisting of about 25 weight percent tung- 9 sten, about 10 weight percent tantalum, about 10 weight percent chromium, less than about 0.50 weight percent carbon, the remainder nickel and incidental impurities.

5. An alloy consisting of about 25 weight percent tungsten, about 10 Weight percent tantalum, about 10 Weight percent molybdenum, less than about 0.50 weight percent carbon, the remainder nickel and incidental impurities.

6. An alloy consisting of about 25 weight percent tung sten, about 10 weight percent tantalum, about 10 weight percent chromium, about 10 weight percent molybdenum, less than about 0.5 Weight percent carbon, the remainder nickel and incidental impurities.

7. An alloy consisting of about 30 weight percent tungsten, about weight percent tantalum, about 5 weight percent iron, less than about 0.50 weight percent carbon, the remainder nickel and incidental impurities.

8. An alloy consisting of about 30 weight percent tungsten, about weight percent tantalum, about 10 Weight percent iron, less than about 0.50 weight percent carbon, the remainder nickel and incidental impurities.

9. An alloy consisting of about 25 weight percent tungsten, about 10 weight percent tantalum, about 10 Weight percent chromium, about 2 weight percent aluminum, less than about 0.50 weight percent carbon, the remainder nickel and incidental impurities.

10. An alloy consisting of about 25 weight percent tungsten, about 10 weight percent tantalum, about 10 Weight percent chromium, less than about 0.15 weight percent carbon, the remainder nickel and incidental impurities.

11. An alloy consisting of about 25 weight percent tungsten, about 10 weight percent tantalum, about l0 weight percent molybdenum, less than about 0.15 weight percent carbon, the remainder nickel and incidental im purities.

12. An alloy consisting of about 25 weight percent tungsten, about 10 weight percent tantalum, about 10 weight percent chromium, about 10 weight percent molybdenum, less than about 0.15 weight percent carbon, the remainder nickel and incidental impurities.

13. An alloy consisting of about 30 Weight percent tungsten, about 5 weight percent tantalum, about 5 weight percent iron, less than about 0.15 weight percent carbon, the remainder nickel and incidental impurities.

14. An alloy consisting of about 30 weight percent tungsten, about 10 Weight percent tantalum, about 10 weight percent iron, less than about 0.15 Weight percent carbon, the remainder nickel and incidental impurities.

15. An alloy consisting of about 25 weight percent tungsten, about 10 weight percent tantalum, about 10 Weight percent chromium, about 2 weight percent aluminum, less than about 0.15 weight percent carbon, the remainder nickel and incidental impurities.

References Cited by the Examiner UNITED STATES PATENTS 1,588,518 6/26 Brace 174 1,807,554 5/31 Rohn 7517l 1,836,317 12/31 Franks 75-l71 2,122,403 7/38 Balke et al 75l76 2,977,225 3/61 Wlodek et al 75-l76 DAVID L. RECK, Primary Examiner.

WINSTON A. DOUGLAS, Examiner. 

1. AN ALLOY CONSISTING ESSENTIALLY OF, ALONG WITH INCIDENTAL IMPURITIES, AT LEAST 25 WEIGHT PERCENT NICKEL, 1 TO 25 WEIGHT PERCENT TANTALUM, 20 TO 50 WEIGHT PERCENT TUNGSTEN, A MAXIMUM OF 0.15 WEIGHT PERCENT CARBON, AND SELECTED AMOUNTS OF AT LEAST ONE METAL CHOSEN FROM THE GROUP CONSISTING OF IRON, ALUMINUM, MOLYBDENUM AND CHROMIUM. 